Với `x \ne [+-1]/2` có:
`P=([4x-x^2]/[1-4x^2]-x):([4x^2-x^4]/[1-4x^2]+1)`
`P=[4x-x^2-x(1-4x^2)]/[1-4x^2]:[4x^2-x^4+1-4x^2]/[1-4x^2]`
`P=[4x-x^2-x+4x^3]/[1-4x^2].[1-4x^2]/[1-x^4]`
`P=[4x^3-x^2+3x]/[1-x^4]`
\(=\left(\dfrac{4x-x^2-x+4x^3}{1-4x^2}\right):\dfrac{4x^2-x^4+1-4x^2}{1-4x^2}\)
\(=\dfrac{4x^3-x^2+3x}{-x^4+1}\)